Ten mature Small East African does weighing 26 "3.2 kg were allocated to two latin
squares to investigate the potential of weather-damaged groundnut hay as a supplement in a
diet for goats. The basal diet offered at 900 g/d/goat consisted of mature veld hay ground
with dried poultry litter and the daily supplements were 0, 135, 270, 405 and 900 g of
groundnut hay. Inclusion of groundnut hay resulted in a decrease in intake of the basal
diet at the rate of 37 g for every 100 g of groundnut hay eaten but total dry matter
intake was increased. The levels of ammonia-nitrogen and volatile fatty acids in the
rumens of the goats were lower than those needed for high ruminant productivity (2-8 mg NH3
- N and 31 - 73 mmole/l). Rumen degradability of the basal diet was not affected by the
amount of groundnut hay offered or eaten but in vivo dry matter digestibilities
were 37, 42, 45, 50 and 55% (sed 1.9) for diets in which 0, 135, 270, 405 and 900 g of
groundnut hay were offered. It was concluded that weather damaged groundnut hay does not
act as a supplement but rather as a substitute for mature veld hay diets given to mature
goats, despite its palatability and content of readily degradable cell wall.

Voluntary feed intake is a major determinant of livestock productivity; limited
voluntary feed intake is a primary constraint to productivity in animals fed forage diets.
Voluntary feed intake of such diets can be improved by grinding and pelleting the forages
but this is often costly and impracticable in African small scale farming systems. There
is therefore a need to find alternative ways of improving intake of forage diets in these
farming systems. This is particularly important since forages are the main sources of
nutrients available to ruminant livestock in most African small scale farming systems.

Supplementation with cereal and/or legume grains has resulted in increased intakes in
intensive livestock production systems and has been the subject of several excellent
reviews including those by Doyle (1987) and Lawrence (1988). However the use of grains to
feed ruminants is undesirable in small scale farming systems as this puts ruminants into
direct competition for food with the human population. Moreover in some areas the
production of these grains is insufficient to support the human population and therefore
the grains would not be available to feed ruminants. Consequently other systems of
supplementation need to be investigated.

Use of forages as supplements has been suggested as an alternative to using grains
(Ndlovu and Buchanan-Smith 1987). Legume forages have readily degradable walls (Van Soest
1982) which would increase substrates available to cellulolytic microbes with a consequent
increase in the population of these microorganisms, if other nutrients are not limiting.
One of the constraints to degradation of forage diets is the small population of
cellulolytic microbes in the rumen ecosystem (Mackie and White 1990). In addition legume
forages supply nitrogen, an essential nutrient for most rumen microbes and minerals.

In Zimbabwe, an abundant source of legume hay is groundnut tops; 71,000 tonnes are
produced annually in the small scale farming systems (Central Statistics Office 1989).
However, the groundnut tops are gathered when mature and the storage facilities are such
that the resultant feed is low in nitrogen but very palatable. The experiments described
here were aimed at investigating the potential of poorly managed groundnut hay as a
supplement in goat diets. Goats are important sources of ready cash and meat to most small
scale farmers in Zimbabwe.

Materials and methods

Animals and design

Ten mature (3 years old) non-pregnant non-lactating does weighing 26"2.8 kg were
used in two 5 (treatments) x 5 (periods) latin squares. The 5 does used in square 1 were
fitted with permanent rumen cannulae. In square 1, the periods were 28 days long - 14 days
to allow the animals to adjust to the treatments and 14 days for data collection. In
square 2, the periods were 17 days long - 10 days for the animals to adjust and 7 days for
measurement of intake and digestibility.

Mature veld hay was mixed with dried deep litter poultry manure from a poultry
enterprise that used veld hay as bedding. The mixture, consisting of 75 parts mature veld
hay and 25 parts dried deep litter poultry manure (w/w), was ground in a hammer-mill to
pass through a 20 mm screen to reduce selection and used as the basal diet in all the
trials. The poultry manure was included to increase the nitrogen content of the basal diet
which was offered at 900 g per goat per day. Treatments consisted of groundnut (Arachis
hypogea) hay, which had been weather-damaged by rain and sun, offered at 135, 270, 405
and 900 g per goat per day in addition to the control with no supplementation.

The chemical composition of mature veld hay, the basal diet and groundnut hay offered
to the goats is shown in Table 1.

Table 1: Chemical composition of the
main ingredients of the diets offered to the goats

Mature

Groundnut

Veld Hay

Basal diet*

Hay

Dry Matter (%)

88.0

89.0

89.0

As % of DM:

Organic matter

87.0

83.0

92.0

Neutral detergent

fibre

65.0

61.0

44.0

N x 6.25

3.4

6.4

7.4

* Basal diet consisted of mature veld hay and dried poultry manure mixed in proportions
of 75:25 (w/w) and milled together such that they were inseparable.

Measurements

Intake and digestibility

The animals were offered both the basal diet and the supplement at 0800 h and any feed
remaining in the troughs was removed before fresh feed was added. The residual feed was
weighed, sub-sampled and stored for chemical analysis. Residual groundnut hay, mainly
stems, was physically separated from veld hay weighed and stored separately. Digestibility
was measured in square 2 using goats in metabolism crates which allowed for separate
collection of faeces and urine.

Rates and extent of fibre degradation

Rumen degradability was measured by incubating nylon bags containing 4 g of the basal
diet, ground by a hammer-mill to pass through a 2 mm screen, in the rumen of fistulated
goats. The bags were removed serially at 3, 6, 9, 12, 24, 48, 60 and 72h post incubation
and washed under clean running tap water until the water obtained by squeezing the bags
was clear. The bags were then oven dried at 60 °C.

Rates of passage

On day 8 of the experimental period in square 1 the goats were dosed with feed marked
with Yb169 at the rate of 1% of dry matter intake. The marker was prepared by soaking
overnight 60 g of the basal diet in 100 ml of distilled water in which 0.15 ml of a 1
micro Curie Yb169 solution had been added and drying at 60 °C in an oven. Faecal grab
samples were collected at 4, 8, 12, 16, 20, 24, 36, 48, 60, 72, 84, 96, 108, and 120h post
dosing. The faeces were oven-dried at 105 °C and then assayed for gamma emission
(counts/g/min) on a Packard Tricarb Scintillation Spectrometer.

Rumen parameters

Rumen fluid was sampled at 0, 4, 8, 12, 16 and 24 h post feeding at the end of each
period in square 1. The pH of the fluid was measured within 2 minutes of collection and
the fluid was stored at -20 °C for analysis of concentrations of rumen ammonia nitrogen
(NH3-N) and types and concentrations of volatile fatty acids (VFAs).

Laboratory analysis

Feed, residual feed and faeces were analyzed for dry matter (DM) and neutral detergent
fibre (NDF); additionally feed was analyzed for organic matter (OM) and nitrogen using
AOAC (1975) recommended methods. Rumen NH3 - N was measured using the method of
Novazamsky et al (1974) while individual concentrations of VFA were determined
using gas liquid chromatography. Total VFA concentration was calculated as the sum of the
concentration of individual VFAs and molar proportions of individual VFAs were calculated
as percentages mol/100 mol of total VFA concentration.

Statistical analysis

Data on intake and digestibility were analyzed using regression techniques and ANOVA
procedures for a 5 x 5 latin square in the MINITAB package which accounted for diet,
animal and period effects.

Rates of digestion were obtained by fitting data on DM and NDF loss from nylon bags to
the non-linear model of Orskov and MacDonald (1979). The equation used was p = a+b(1-e-ct)
where "p" = amount lost at time "t" and "a" is the readily
available fraction, "b" is potentially degradable fraction whilst "c"
is the rate of degradation of the "b" fraction. The constants "a",
"b", and "c" from the above equation derived for each animal in each
period were tested for diet, animal and period effect using ANOVA procedures for a 5 x 5
latin square in the MINITAB package.

Rates of passage from the rumen were obtained by fitting data on faecal counts per g
per min to the non-linear model of Grovum and William (1973)

y = Ae -k1(t-TT) - Ae -k2(t-TT)

where k1 is the rate of passage from the rumen, k2 is the rate of passage from the
post-ruminal compartment, TT is transit time and "y" is counts per gram per
minute at time t. The k1 values obtained were then analyzed for diet, animal and period
effect as described for other data.

For rumen parameters, the data were meaned across the sampling times in each period for
each diet per animal. The 24 h means were then tested for diet, period and animal effect
using 5 x 5 latin square ANOVA as described above.

Level of groundnut hay offered did not affect (P>0.05) the readily degradable
fraction, extent of digestion and rate of digestion of the basal diet (Table 3). Rate of
passage was increased (P<0.005) by 94 and 161% over the control when groundnut hay was
offered at 405 and 900g/d, respectively. The other levels of offer did not significantly
(P>0.05) affect the rate of passage (Table 3).

Rumen parameters

Though the data were collected at 4h intervals over a 24h period, the results are
presented as means for a 24h period since the animals had food available all the time and
feeding occurred intermittently throughout the 24h period.

The pH levels were generally high for all diets (mean 6.6, Table 4) with groundnut
level offer of 405 g resulting in the highest pH. Rumen ammonia levels were low (mean 4.22
mg/100 ml Table 4). Only goats offered groundnut hay at 405 g/d had ruminal ammonia
concentrations that differed significantly (P<0.05) from those of the control diet
(Table 4).

Concentration of VFA was not affected (P>0.05) by level of groundnut hay offered
except at the 900 g level (Table 4). Acetate: Propionate ratios based on molar proportions
(Table 4) were: 7.90, 6.98; 4.95; 6.35 and 5.60 for 0, 135, 270, 405 and 900 g of
groundnut hay offered, respectively. Higher chain VFA made up approximately 20% of the
total VFAs for all diets (Table 4).

Discussion

A supplement is a feed that will increase total intake whilst maintaining or increasing
intake of the basal diet (Kempton 1977). Recommendations for supplementation of poor
quality roughages have emphasized nitrogen supply (Preston and Leng 1984) but there is
evidence that a source of readily degradable fibre can result in increased intakes of poor
quality roughage diets (Ndlovu and Buchanan-Smith 1987). In our experiment, the intake of
the basal diet decreased by 37 g with every 100 g increase in intake of groundnut hay.
Thus groundnut hay served as substitute food rather than a supplement. The preference of
goats for the groundnut hay was probably due to a readily degradable cell wall of the
groundnut hay compared to that in the basal diet. The crude protein content of the two
feeds was not sufficiently different to account for the preference (Table 1). Substitution
of basal diet by legume crop residues has been found by other workers working with cereal
crop residues as basal diets (Mosi and Butterworth 1983; McMeniman et al 1988; Adu et
al 1992; Ngwa and Tawa 1992). Digestibility of dry matter, cell wall and organic
matter increased with increasing level of groundnut hay consumed (Table 2). This increase
was probably due to the fact that cell walls of leguminous forages are more degradable
than cell walls of grasses (Van Soest 1982).

Assuming a value of 15.6 MJ of ME/kg digestible OM (ARC 1984), the ME available from
the diets consumed by the goats was 2.25, 2.62, 3.39, 4.02 and 7.08, MJ/d respectively for
groundnut hay offered at 0, 135, 270, 405 and 900 g. The intakes were therefore below the
maintenance requirements of mature does based on a value of 0.48 MJ/d/kg0.75
(Hatendi et al 1990) except for the highest level of groundnut hay offered. This
occurred even though the basal diet was offered in large amounts that allowed for maximum
refusal (refusal rates of basal diet ranged from 49% with no groundnut hay offered to 83%
with 900 g groundnut hay on offer).

The mean ruminal NH3-N levels obtained in our study were, in the main, low.
It is possible that the goats selected against the poultry litter. Unfortunately the crude
protein content of the refusals was not measured. Nonetheless, the rumen NH3-N
levels obtained in our study were similar to those obtained by Gelaye etal
(1990) and Gelaye and Amoah (1991) when diets containing peanut hay were fed to goats.
Ruminal pH was within the optimal range of 6.0 - 7.0 for cellulolytic bacterial activity
(Hespell and Bryant 1979) while total volatile fatty acid concentrations (Table 4) were
low except at the highest level of groundnut hay offered. This was consistent with data on
intake and digestibility (Table 2). The molar proportions of acetate were higher than
those obtained by Gelaye et al (1990) and Gelaye and Amoah (1991) using peanut hay
diets. The proportions of propionate in the rumen liquid were low compared to the results
of Gelaye and coworkers. This low propionate in the products of digestion of our diets
could constrain goat productivity as propionate has been shown to be the major glycogenic
fatty acid in ruminants (Preston and Leng 1987). However, the diets used in our experiment
resulted in higher proportions of branched chain volatile fatty acids than has been
obtained by other workers using low quality roughages (Chiema et al 1991). The
cause of these high levels was not determined but could be linked to ruminal lysis of
microbes and fermentation of microbial cells.

The degradation values obtained in this study were within the range reported for
similar feeds by Abate and Kiflewalid (1992) and are typical of fibrous feeds. It is
noteworthy that the parameters were not affected by increases in groundnut hay intake. On
the other hand, in vivo apparent dry matter digestibility was affected by level of
groundnut hay intake. This fact further buttresses arguments against using nylon bag
degradation values for predicting in vivo digestibility of low quality diets
(Orskov 1989).

Conclusion

At high levels of offer, poorly managed groundnut hay and mature veld hay were consumed
in quantities sufficient to meet maintenance energy requirements of adult Small East
African goats. This, however, was achieved by substituting for the basal diet and not by
supplementing it. Digestibility of total dietary nutrients improved with increasing levels
of groundnut hay consumed but degradation kinetic parameters were not affected.

Acknowledgements

This work was funded by the Southern African Coordination Conference on Agricultural
Research (SACCAR) Small Research Grant Number SRG-22 and the University of Zimbabwe
Research Board.

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